I put polycrylic on my boards, probably 8 coats in all. I sand indeed with 320 after 4 coats. I made novice mistakes along the way, brushing too late leaving marks as it dried etc, but worked them out with some sanding and coats.

I wanted a nice semi-gloss smooth finish. I boat a high grit sandpaper kit going from 1200 to 12000. I sanded wet and noticed the boards, while getting smooth, we getting milky in spots. I tried a auto compound to clean this up but it did t work.

Any thoughts?

It's cured for over a week so that's not it and I'm certain this is dry so the milk isn't from a new coat...

Ditch the high grit sanding kit. Cornhole boards are not what they were designed for. There is no need for wet sanding in any case much less over poly that I'm guessing wasn't fully cured. A weeks curing time isn't necessarily enough time to fully cure, especially with 8 coats.

Poly is and will always be a love hate relationship. Period. So...do lay down with a foam brush three coats. Do sand with 220 after third or fourth coat. Do take your time. Do not over brush. Do not clear foam brush of poly back into container. It'll introduce air bubbles into poly. Do pay attention to temperature and humidity. Do not wet sand. No need. Do make sure poly is fully dry before applying another coat. Do work one full row at a time lengthwise. Do not try to lay down poly too thick. Do apply at least seven coats. It's a great number for a good build. Do take orbital sander with 220 after 6th coat and make sure you are perfect for your last 7th coat.

Kbux wrote:Having been thwarted by polycrylic many a time I'm trying to learn here:Why sand between those certain coats of poly?What is ideal temperature/humidity?Thanks in advance!

A couple hundred sets in and I still don't have poly figured out that well. Here are my two cents.

I don't sand in between coats if I don't have to, and I almost never ever over a wrap set, I usually do only on sets with natural wood showing, they seem to need it.

Ideal temps, I don't like to do anything belowing 70 degrees here in so cal as I have had funny stuff happen.

Humidity, I am absolutely convinced anything above 50% humidity in my set up, the poly looks terrible with all the funny things it does that look like orange peel, or crystally, or however you want to describe it, but yeah, anyone that works with poly knows what I am talking about.

-Tom

Last edited by chevellesb406 on Wed Nov 09, 2016 11:13 am, edited 1 time in total.

I have commented on this a number of times in the past, and is only my opinion. Some of this may be a bit off point but will hopefully help some of the builders running into issues.

First, Minwax Polycrylic is overrated and way too expensive at around $50/gal (+/-). Comparatively, Rust-Oleum Ultimate Polyurethane (water based) is around $31-32/gal and I find it to be the better product of the two. About two years ago when Lowe's stopped carrying Rustoleum I made a few calls to their corporate HQ to find out who might be carrying it in my area but didn't come up with anything solid. They suggested that I try another of their products, Parks PRO Finisher Water-Base Polyurethane which is available at both Home Depot and some Lowe's stores at around $38/gal and is now what I use exclusively. While not as cheap as their Ultimate Poly, it still beat Minwax Polycrylic by $10-12/gal. At one point I spoke with one of their technical folks who told me that the Parks poly was developed strictly for hardwood floors and when cured is harder than both their Ultimate poly and Minwax polycrylic and, didn't yellow. I found that last part to be somewhat dubious thinking that hardwood floors are not in direct sunlight like cornhole boards.

I've read numerous posts here touting Polycrylic as non-yellowing. Wrong! In the end it all yellows to some degree, at least in this application. And if you take the time to read all that really small print on the can, it will say that it in fact does. I decided to do an experiment to see how much yellowing does occur.

I took a 2'x2' piece of plywood scrap from an old cabinet project, divided into 6 sections and painted 3 sections white and the rest random colors. I applied some random vinyl shapes to each section. I poly'd each section like I normally would with a set of boards, with Minwax Polycrylic, Rustoleum Ultimate and Parks Pro Finisher. Throughout the spring and summer of 2015 I religiously put the test board in direct sunlight most every day, all day. By the end of last summer I took all the vinyl off to see which ones yellowed the worst. Before the vinyl came off you could tell there was yellowing. It was hard to really see any serious yellowing over the colored sections though it was there to some degree, but the white sections told an entirely different story.

Of the 3, the highly touted, highly expensive Minwax Polycrylic yellowed the worst. The Rustoleum Ultimate had a fair amount of yellowing but not near as bad as the Minwax. The Parks Pro Finisher was the best of the three with hardly any serious yellowing, but some to a smaller degree. While I realize this isn't scientific by any means, it showed me what I already pretty much knew.

Sanding between coats isn't always necessary but can help. I pretty much always hand sand the final coats with either 320 or 400 grit paper before the final coat. A random orbital sander is too aggressive, especially over graphics. Because I spray it's generally not necessary to do much sanding.

High humidity can be a real problem sometimes. High humidity will almost always cause the poly to cure with a milky look to it that cannot be sanded out. This is most obvious over dark colors. With white or over natural wood, not so much unless that natural wood has a dark stain. If you spray your poly that problem becomes bigger because the atomized poly is picking up moisture before it hits the wood. I had a few disasters before I learned that lesson. I don't spray much above 60% humidity unless I am really pressed to get a set out. Because I don't offer fully painted sets anymore in favor of stained sets (except for the painted frames), I will sometimes spray in higher humidity. Temps below 60 can be problematic as well and is probably below the recommended temps for proper use.

I have also noticed many differences of opinion when it comes to full wraps. Some will laminate while others poly. The graphics company I deal with for all my graphics tell me that poly over graphics is better vs. laminated graphics. While it is a matter of opinion, they've been in business for 30 years so I respect their professional opinion. It's not an issue for me any more as they print all my graphics directly to my board decks. I no longer have to use near the amount of poly I used to have to use to fully cover vinyl graphics. I have cut the amount of poly I now use on a set of boards by 2/3.

Great post Pharaoh. I completely agree on using the Parks PRO Finisher. I switched about two years ago as well. I am fortunate that I rarely if ever have humidity to contend with living in Colorado. Plus I have a basement workshop so temperature is not an issue. I spray as well and love the results. Personally I usually only have to do a light sanding with 220 grit between coats 3 and 4. Each coat for me is more like two coats as I liberally spray the decks from each long side on each coat.

pharaoh wrote:I have commented on this a number of times in the past, and is only my opinion. Some of this may be a bit off point but will hopefully help some of the builders running into issues.

First, Minwax Polycrylic is overrated and way too expensive at around $50/gal (+/-). Comparatively, Rust-Oleum Ultimate Polyurethane (water based) is around $31-32/gal and I find it to be the better product of the two. About two years ago when Lowe's stopped carrying Rustoleum I made a few calls to their corporate HQ to find out who might be carrying it in my area but didn't come up with anything solid. They suggested that I try another of their products, Parks PRO Finisher Water-Base Polyurethane which is available at both Home Depot and some Lowe's stores at around $38/gal and is now what I use exclusively. While not as cheap as their Ultimate Poly, it still beat Minwax Polycrylic by $10-12/gal. At one point I spoke with one of their technical folks who told me that the Parks poly was developed strictly for hardwood floors and when cured is harder than both their Ultimate poly and Minwax polycrylic and, didn't yellow. I found that last part to be somewhat dubious thinking that hardwood floors are not in direct sunlight like cornhole boards.

I've read numerous posts here touting Polycrylic as non-yellowing. Wrong! In the end it all yellows to some degree, at least in this application. And if you take the time to read all that really small print on the can, it will say that it in fact does. I decided to do an experiment to see how much yellowing does occur.

I took a 2'x2' piece of plywood scrap from an old cabinet project, divided into 6 sections and painted 3 sections white and the rest random colors. I applied some random vinyl shapes to each section. I poly'd each section like I normally would with a set of boards, with Minwax Polycrylic, Rustoleum Ultimate and Parks Pro Finisher. Throughout the spring and summer of 2015 I religiously put the test board in direct sunlight most every day, all day. By the end of last summer I took all the vinyl off to see which ones yellowed the worst. Before the vinyl came off you could tell there was yellowing. It was hard to really see any serious yellowing over the colored sections though it was there to some degree, but the white sections told an entirely different story.

Of the 3, the highly touted, highly expensive Minwax Polycrylic yellowed the worst. The Rustoleum Ultimate had a fair amount of yellowing but not near as bad as the Minwax. The Parks Pro Finisher was the best of the three with hardly any serious yellowing, but some to a smaller degree. While I realize this isn't scientific by any means, it showed me what I already pretty much knew.

Sanding between coats isn't always necessary but can help. I pretty much always hand sand the final coats with either 320 or 400 grit paper before the final coat. A random orbital sander is too aggressive, especially over graphics. Because I spray it's generally not necessary to do much sanding.

High humidity can be a real problem sometimes. High humidity will almost always cause the poly to cure with a milky look to it that cannot be sanded out. This is most obvious over dark colors. With white or over natural wood, not so much unless that natural wood has a dark stain. If you spray your poly that problem becomes bigger because the atomized poly is picking up moisture before it hits the wood. I had a few disasters before I learned that lesson. I don't spray much above 60% humidity unless I am really pressed to get a set out. Because I don't offer fully painted sets anymore in favor of stained sets (except for the painted frames), I will sometimes spray in higher humidity. Temps below 60 can be problematic as well and is probably below the recommended temps for proper use.

I have also noticed many differences of opinion when it comes to full wraps. Some will laminate while others poly. The graphics company I deal with for all my graphics tell me that poly over graphics is better vs. laminated graphics. While it is a matter of opinion, they've been in business for 30 years so I respect their professional opinion. It's not an issue for me any more as they print all my graphics directly to my board decks. I no longer have to use near the amount of poly I used to have to use to fully cover vinyl graphics. I have cut the amount of poly I now use on a set of boards by 2/3.

Hi Pharaoh,Thanks for the post, I appreciate you taking the time to write that out. I personally buy my poly usually at 40% off so price isn't my motivator to switch, but I am going to try out this Parks Pro if it doesn't do as much weird stuff and the yellowing and durability comparison is interesting. I went to your link and looked at your gallery and just wanted to tip my hat to a fellow builder, I find your designs clean, precise, and really stand out, I love your style, the inspiration factor is up there, I miss seeing people regularly posting their work, but understand the many reasons many of us have kinda pulled back on the reigns of doing exactly that. Anyway, a tip of my hat, and thanks again on both fronts. Only slightly jealous you have a local printer that can print straight to your decks, that would be awesome, but not really an option I have found for me yet out here.

Hi Pharaoh,Thanks for the post, I appreciate you taking the time to write that out. I personally buy my poly usually at 40% off so price isn't my motivator to switch, but I am going to try out this Parks Pro if it doesn't do as much weird stuff and the yellowing and durability comparison is interesting. I went to your link and looked at your gallery and just wanted to tip my hat to a fellow builder, I find your designs clean, precise, and really stand out, I love your style, the inspiration factor is up there, I miss seeing people regularly posting their work, but understand the many reasons many of us have kinda pulled back on the reigns of doing exactly that. Anyway, a tip of my hat, and thanks again on both fronts. Only slightly jealous you have a local printer that can print straight to your decks, that would be awesome, but not really an option I have found for me yet out here.

-Tom

Thanks for the kind words.

One thing I forgot to mention in my post, although I've commented before on other threads concerning poly, is that I always use semi-gloss. The only time I've used gloss was when I couldn't get any semi at the moment. Personally, I have never liked the super shiny high gloss look on my boards. It may add some wow factor for the customer but it's not for me. I try and make my finishes as flawless as possible but if there is a small smudge, or a run or something that that may be less than perfect, it doesn't show up as bad with semi gloss as it does with gloss. I hit the 700 set mark this past summer and 99% have been with semi gloss.

The graphics company I use for my graphics are some great folks who I've dealt with from my start in 2008. Except for one or two exceptions they have produced all of my full color graphics and single color vinyl graphics until I purchased my own vinyl cutter. Once they moved to a larger facility and got a big flatbed printer they were the ones who suggested I have my graphics printed directly to the boards. Now, the only time I use vinyl of any sort is for single color designs. But, that is probably only a plus for me as I'd venture to say that a large percentage of graphics companies wouldn't do that for the average builder unless they have a relationship of some sort with him. They probably wouldn't do the work because they are not using their substrate, which is understandable. That's why they are in business.

I have been using minwax poly acrylic satin for 5 years never had a problem. To me the gloss makes the board to slick. I have never had a complaint about the satin finish. I put 5 to 6 coats ( foam brush) then DRY sand lightly with 400 or 300 grit. As far as the price for a gal. of the poly it is $50.00 but If you have a sherwin Williams Paint store near you they run 40% off sales a couple times a year. I stock up when they do. You can get a gal. on sale there for $28.00

Oldlures wrote:I have been using minwax poly acrylic satin for 5 years never had a problem. To me the gloss makes the board to slick. I have never had a complaint about the satin finish. I put 5 to 6 coats ( foam brush) then DRY sand lightly with 400 or 300 grit. As far as the price for a gal. of the poly it is $50.00 but If you have a sherwin Williams Paint store near you they run 40% off sales a couple times a year. I stock up when they do. You can get a gal. on sale there for $28.00

yep, Sherwin Williams, I get about 10 gallons every time they have the 40% sale, its a life saver. Speaking of, didn't get any at the last sale and down to my last couple of cans, I will be on the look out for the next one.

I am having a very frustrating issue. I painted my boards, applied a couple coats of poly, sanded them(took some paint off somehow), applied the vinyl wrap and coated it 6 times with poly satin. again, I tried to lightly sand it with 1200 grit and on the very first slide of the paper I damaged the vinyl. how does that even happen? after 6 coats, dried for 24 hours each coat, and its like I never even applied it in the first place. now I'm pissed and extremely disappointed because these boards were going to be a gift for friend to honor his service in the airforce.

sawalker1986 wrote:I am having a very frustrating issue. I painted my boards, applied a couple coats of poly, sanded them(took some paint off somehow), applied the vinyl wrap and coated it 6 times with poly satin. again, I tried to lightly sand it with 1200 grit and on the very first slide of the paper I damaged the vinyl. how does that even happen? after 6 coats, dried for 24 hours each coat, and its like I never even applied it in the first place. now I'm pissed and extremely disappointed because these boards were going to be a gift for friend to honor his service in the airforce.

Could you post a pic of the damage? That might help determine what exactly happened. What method are you using for poly application? Foam brush, spraying?